The invention relates to a device for filtering liquids. Such a device is described for example in DE 100 19 672 A1.
Devices of this kind serve the cross-flow permeation of free-flowing media. They contain at least two shafts, onto which in each case many disk-shaped diaphragm bodies are arranged parallel to each other and in mutual distance. The shafts are hollow, and the diaphragm disks are made of ceramic material and are burred with radial channels. Between the radial channels and the inside of the hollow shaft is a conducting connection. The liquid to be filtered arrives from the outside through the porous material of the diaphragm body into the channels, and from there into the hollow shaft.
The shafts mentioned run parallel to each other, so that also the diaphragm disks of two each other adjacent disk stacks are arranged parallel to each other. The shafts are arranged so close next to each other in such a manner that the disks of two disk stacks interlockingly engage.
The disks do not have to have the mentioned design using porous ceramic material. There are also applications in which some disks are built up as so-called dummy disks. It is also possible to make the disks from strainer bodies. Also combinations of the designs mentioned are conceivable, for example the combination of strainer body-diaphragm body. In the following description only the term “disks” is used.
In order to achieve as great a productivity as possible, as many disks as possible are to be positioned on a shaft. The disks therefore must be arranged as close as possible. On the other hand however it must be made certain that the disks of one stack do not touch the disks of the other stack. Therefore an accurate axial positioning of the disks on their shafts is required.
For the purpose of positioning, distancing elements are arranged between adjacent disks. Also for the purpose of an accurate axial positioning the total disk stack is compressed, for example by a nut, which is screwed onto the hollow shaft on one of its ends, and which exerts a suitable pressure on the multiplicity of disks with the distancing elements present between them. A spring assembly can be mounted between the nut and hollow shaft.
Furthermore it must be ensured that the disks are positioned perfectly also in the radial direction, and that with the rotation of the shaft with the disks present on it concentricity is ensured and radial deflecting is avoided. Furthermore it must be ensured that the torque is transferred from the rotating hollow shaft equally onto all disks of the hollow shaft.
Finally a perfect seal between the disks and the distancing elements must be provided, so that no liquid passes through between the disks and the distancing elements to the hollow shaft.
All these requirements could not be fulfilled to the desired extent with the well-known devices.